METHOD FOR DETECTING A FUEL LEAK IN A HIGH-PRESSURE FUEL INJECTION SYSTEM

Abstract

The invention provides a method for detecting an external fuel leak in a high-pressure fuel injection circuit (130, 128, 120, 132) comprising a pump (130), a supply rail (120), at least one injector (132), a pressure sensor (25) in the rail (120), a computer (10) configured to generate pump (130) activation events, the method being implemented during an injection cut-off phase and comprising steps consisting of comparing a pressure value measured by the sensor with a fuel pressure setpoint value; and if the measured value is less than the setpoint value, operating the high-pressure pump (130) in order to bring the measured value back to the setpoint value by triggering at least one pump event and incrementing a pump event counter by at least one unit until the measured value is greater than or equal to the setpoint value.When the pump event counter value exceeds a threshold value, the process generates an alarm indicating a fuel leak. See Figure 1 for the abbreviation.

Description

Title of the invention: METHOD FOR DETECTING A FUEL LEAK IN A HIGH-PRESSURE FUEL INJECTION CIRCUIT Technical field of the invention

[0001] The present invention relates to a method for detecting an outward fuel leak in a high-pressure fuel injection circuit. The invention also relates to a computer for implementing the process and an internal combustion engine comprising such a computer. Technical background

[0002] The invention relates to the detection of fuel leaks to the outside in a high-pressure supply circuit of an internal combustion engine such as, for example, a diesel engine, or a dual-fuel engine, for example based on gasoline and liquefied petroleum gas (LPG) of a motor vehicle, or even an internal combustion engine integrated into a so-called "hybrid" propulsion system.

[0003] An injection engine classically includes a fuel injection circuit, also called a high-pressure circuit, comprising a high-pressure pump adapted to put the fuel under high pressure (for example, on the order of 100 bar), one or more fuel injectors in a combustion chamber, and an injector supply rail, which carries the fuel from the outlet of the high-pressure pump to the injectors.

[0004] In the context of controlling a high-pressure system of a combustion engine using dual fuel, functions for monitoring the behavior of the high-pressure fuel system are necessary to meet the requirements for supervising the operation of the whole.

[0005] For this type of system, and in particular for safety reasons, it is necessary to have the ability to alert the user in the event of an external fuel leak.

[0006] Such an external leak is a leak of fuel to the outside of the high-pressure fuel injection circuit.

[0007] The particular case of dual-fuel operating modes includes, in particular, operating cases which are not controlled by the diagnostic functions available in the generic version of the pressure control system.

[0008] Indeed, in the event of operation in pure LPG mode, the high-pressure pump for gasoline injection can continue to operate to satisfy a setpoint of the required high pressure in order to anticipate and prepare for the resumption of gasoline injection or dual-fuel operation.

[0009] During such a phase, if a fuel leak to the outside is present, it is amplified and continues because the control function of the high-pressure pump tends to compensate for the pressure loss induced by the fuel leak.

[0010] Currently, the diagnostics used to detect a fuel leak make it possible to determine an external leak, problems with mechanical components of the high-pressure system, problems with mechanical components of the low-pressure system, or leaks at the injectors.

[0011] These diagnostics are based on the analysis of the difference between the pressure setpoint that should prevail in the high-pressure circuit, for example in the injector supply rail, and the actual pressure whose value is known thanks to a pressure measuring sensor.

[0012] A leak detection device in a high-pressure fuel injection circuit is known from document DE102013101850, which includes a fuel pressure sensor in the circuit, and a leak detection circuit that analyzes the shape of the output signal from the fuel pressure sensor in the circuit, to determine a fuel injection period, and to determine a leak based on a pressure variation in the fuel injection circuit during an injection period, and over a longer period of time including the injection period.

[0013] In the case of a dual-fuel engine, for example when the engine is operating in pure LPG mode, such types of diagnostic procedures cannot be implemented because they require high-pressure pump activity and injection.

[0014] Indeed, during operation in LPG mode, conventional gasoline injection is deactivated. Normally, the fuel pressure in the rail remains stable, but this behavior may be slightly different.

[0015] Pressure can indeed: - increase due to thermal phenomena, because the fuel's temperature increases in an enclosed space, and therefore its pressure increases; - decrease by the same thermal phenomenon if the fuel temperature decreases; - decrease due to internal leaks in the system that are tolerated such as leaks from the outlet valve or the pressure reducing valve.

[0016] Since the temperature information is not sufficiently precise because it comes from a model and internal leaks can vary from one component to another, it is not possible to base an external leak diagnosis directly on variations in pressure value.

[0017] Known diagnostic methods do not allow for the detection of possible fuel leaks to the outside when the injection is inactive. Summary of the invention

[0018] The invention proposes a method for detecting an external fuel leak in a high-pressure fuel injection circuit in an internal combustion engine comprising: - a high-pressure pump; - at least one fuel injector; - a fuel supply rail extending between the outlet of the high-pressure pump and each of at least one fuel injector; - a sensor for measuring the pressure value in said rail; - a computer configured to generate pump events, each representative of an activation of the high-pressure pump; the process being implemented during an operating phase in which fuel injection through said injection circuit is cut off, and the process comprising the following cycle of steps: - E3 compare a value of the pressure measured by the sensor, noted VPM, with a setpoint value of the fuel pressure in the rail, noted VPC; - E4) if VPM is less than VPC, operate the high-pressure pump to bring the measured pressure value VPM back to the setpoint pressure value VPC, by triggering at least one pump event and incrementing a pump event counter by at least one unit per pump event until VPM is greater than or equal to VPC; and - E8) when the value of the pump event counter exceeds a threshold value generate an alarm indicating a fuel leak.

[0019] According to other features of the process: - when for a specified period, no pump event is triggered, the process includes a step E6) of decrementing the pump event counter by at least one unit per specified period without a pump event; - the process is implemented during each interruption of fuel injection by said fuel injection circuit; - prior to the implementation of said cycle of steps, the process includes a step E7) of initializing the value of the pump event counter; - Each pump event is an activation of the high-pressure pump for at least a short duration.

[0020] The invention also proposes a computer characterized in that it is configured to implement a method for detecting a fuel leak according to the invention. The invention further proposes an internal combustion engine comprising a high-pressure fuel injection circuit including: - a high-pressure pump; - at least one fuel injector; - a fuel supply rail extending between the outlet of the high-pressure pump and each of at least one fuel injector; - a sensor for measuring the pressure value within said rail, - and a computer configured to implement a method for detecting a fuel leak to the outside in said circuit according to the invention.

[0021] According to other characteristics of the combustion engine: - it includes a dual fuel injection system; - it includes a dual injection system, direct for gasoline and indirect for liquid gas, in particular liquefied petroleum gas (LPG). Brief description of the figures

[0022] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which:

[0023] [Fig.1] - the [Fig.1] is a schematic representation of a set of double injection, direct and indirect, of fuels into the cylinders of a gasoline and LPG combustion engine;

[0024] [Fig.2] - [Fig.2] is a schematic representation of the steps of a fuel leak detection process according to an example of an embodiment of the invention;

[0025] [Fig.3] - [Fig.3] is a diagram illustrating an example of variation of different parameters during the implementation of the process. Detailed description of the invention

[0026] In the description that follows, identical, similar or analogous elements will be designated by the same reference numerals.

[0027] A dual injection system 1 of known general design has been schematically represented in [Fig.1].

[0028] In the system, gasoline is transferred from a tank 112 by a low pressure pump 114 which is for example an electric pump capable of compressing the fuel for example to a pressure of about 5 bar.

[0029] The high-pressure zone includes a supply rail 120 connected to a pipe 128 equipped with a high-pressure pump 130 (for example, with piston(s) actuated by at least one cam of a camshaft of the combustion engine equipped with such a double injection system) whose function is to increase the low pressure of approximately 5 bar prevailing in the supply line 116 to a high pressure, for example, equal to approximately 100 bar.

[0030] The fuel, for example gasoline, is then injected directly into each of the cylinders not represented of the internal combustion engine by a series of high-pressure injectors 132 ensuring direct injection from the high-pressure fuel rail 120.

[0031] The supply line 116 can be equipped with a pressure regulator 122 which maintains the pressure in the supply line 116 at a practically constant value.

[0032] The low pressure zone 118 includes a pipeline 124 which is directly connected to an LPG gas tank 113.

[0033] A low pressure zone 118 is here in the form of a low pressure tubular rail, which is connected to a series of low pressure injectors 126 which inject "gaseous" fuel into the intake duct, not shown, of the internal combustion engine.

[0034] Alternatively, the low-pressure zone may include only one low-pressure injector which injects fuel into the intake duct.

[0035] The intake duct is connected to the various combustion chambers, not shown, of the cylinders of the internal combustion engine.

[0036] For the implementation of the method according to the invention of detecting a fuel leak to the outside, here in the high-pressure fuel injection circuit (130, 128, 120, 132) (also referred to under the terminology of high-pressure circuit), a sensor 25 is also provided for measuring the value of the pressure prevailing in the supply rail 120.

[0037] The leak detection system 1 also includes at least one computer 10, which may be a controller, microcontroller, processor, microprocessor, FPGA, or any other electronic component configured for the implementation of the leak detection method described below.

[0038] With reference to [Fig.2], we will now describe the leak detection method implemented according to the invention.

[0039] The process is only implemented if the engine is running, which is checked by the computer 10 during a preliminary step E0, for example but not limited to, from a non-zero value of the engine speed Rpm.

[0040] By way of non-limitation, the method preferably includes a step El of verification, by the computer 10, that the operating context of the engine allows the implementation of a fuel leak detection.

[0041] This step may, for example, include checking the following elements: - the engine speed value; - the quantity of fuel injected; - the setpoint value of the pressure gradient of the injected fuel; - the time elapsed since start-up and the VPC setpoint value of the fuel pressure in rail 120.

[0042] The system must have been adapted at least once since its inception, the adaptation aimed at eliminating the dispersion that may appear between several components on different vehicles.

[0043] If the check carried out in step E1 is positive, during a step E2, the computer 10 determines whether the engine is in a phase of its operation during which fuel injection through the injection circuit is cut off.

[0044] If the computer 10 determines that the engine is in a stable injection cut-off period, during a step E3, the computer 10 performs a comparison between a VPM value of the pressure measured by the sensor 25 with a VPC setpoint value of the fuel pressure in the rail 120.

[0045] If VPM < VPC, during a step E4, the control unit 10 causes the high-pressure pump 130 to start up by: - triggering at least one initial EP pump event; and - causing an E5 increment of a CEP pump event counter of at least one unit for each EP pump event triggered per time segment.

[0046] If VPM remains less than VPC, step E4 is repeated in a loop as a series of EP pump events until VPM >= VPC.

[0047] When the VCEP value of the pump event CEP counter is greater than a determined threshold value VCEPseuil (VCEP > VCEPseuil), during a step E8, the computer 10 then generates an alarm, or alert, which may be an audible or visual alarm.

[0048] For example, the leak detection system 1 may include an interface such as a screen or indicator light 11, which may illuminate or display a warning message during step 120 to draw the vehicle driver's attention to the detected leak. For example, a dashboard indicator light may illuminate and / or a message may appear on the vehicle's central display, indicating the detection of a leak and urging the driver to stop as soon as possible to have the vehicle checked. In some embodiments, step E8 may also include the vehicle adopting a degraded engine operating mode and / or limiting the vehicle's speed until the vehicle is taken to a service and maintenance center.

[0049] When for a specified time T no EP pump event is triggered by the computer 10, the computer 10 causes a decrement E6 of the CEP pump event counter of at least one unit.

[0050] Prior to its implementation, the method may include a step E7 for initializing the VCPE value of the CPE pump event counter.

[0051] In [Fig.3], as a function of the elapsed time indicated on the x-axis, the following has been represented from the bottom up : - variations in the measured value of VPM; - the VPC setpoint value; - variations in engine speed (RPM); - variations in the CEP counter of pump events representative of the activation of the high-pressure pump.

[0052] As can be seen, when the measured value VPM is less than the threshold value VPC, the pump is activated - here three times consecutively - with a corresponding increment of three units of the VCEP value of the CEP counter.

[0053] Then, for a determined period T, VPM remains greater than VPC, resulting in a decrement of one unit of the CEP counter.

Claims

Demands

1. A method for detecting an external fuel leak in a high-pressure fuel injection circuit (130, 128, 120, 132) in an internal combustion engine comprising: - a high-pressure pump (130); - at least one fuel injector (132); - a fuel supply rail (120) extending from the outlet of the high-pressure pump (130) to each of at least one fuel injector (132); - a sensor (25) for measuring the pressure value in said rail (120); - a computer (10) configured to generate pump events (PEs), each representative of an activation of the high-pressure pump;the method being implemented during an operating phase in which fuel injection through said injection circuit is cut off, and the method comprising the following cycle of steps: - E3 compare a value of the pressure measured by the sensor, denoted VPM, with a setpoint value of the fuel pressure in the rail (120), denoted VPC; - E4) if VPM is less than VPC, operate the high-pressure pump (130) in order to bring the measured pressure value VPM back to the setpoint value of the pressure VPC, by triggering at least one pump event (EP) and by incrementing (E5) a pump event counter (CEP) by at least one unit per pump event (EP) until VPM is greater than or equal to VPC; and - E8) when the value (VCEP) of the pump event counter exceeds a threshold value (VCEPthreshold), generate an alarm indicating a fuel leak.

2. A method according to claim 1, characterized in that, when for a specified time (T) no pump event (EP) is triggered, the method includes a step E6) of decrementing the pump event counter (CEP) by at least one unit per specified time (T) without a pump event (EP).

3. A method according to any one of the preceding claims, characterized in that it is implemented during each cut of fuel injection by said fuel injection circuit (130, 128, 120, 132).

4. A method according to any one of the preceding claims, characterized in that, prior to the implementation of said cycle of steps, it includes a step E7) for initializing the value of the pump event counter (PEC).

5. A method according to any one of the preceding claims, characterized in that each pump event (PE) is an activation of the high-pressure pump (130) for at least a short time.

6. Calculator (10), characterized in that it is configured to implement a method for detecting a fuel leak according to any one of claims 1 to 5.

7. Internal combustion engine comprising a high-pressure fuel injection circuit (130, 128, 120, 132) including: - a high-pressure pump (130); - at least one fuel injector (132); - a fuel supply rail (120) extending between the outlet of the high-pressure pump (130) and each of at least one fuel injector (132); - a sensor (25) for measuring the value (VPC) of the pressure in said rail (120), - and a computer (10) configured to implement a method for detecting an external fuel leak in said circuit according to any one of claims 1 to 5.

8. Combustion engine according to the preceding claim, characterized in that it comprises a double fuel injection assembly.

9. Combustion engine according to the preceding claim, characterized in that it comprises a double injection system, direct of gasoline (130, 128, 120, 132) and indirect (113, 124, 118, 126) of liquid gas, in particular liquefied petroleum gas LPG.

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